Activated ras oncogene transfection into suitable recipient cells has been shown to induce the metastatic phenotype (Thorgeirsson et al., Mol. Cell Biol. 5: 259-262, 1985). With R. Pozzatti and G. Khoury, we extended this work to rasH transformed rat embryo cells. These cells were also highly metastatic when transformed either by rasH or by rasH linked to an enhancer. However, when the cooperating oncogene Ela was used in conjunction with rasH, metastasis was only rarely seen. We have used this model system to study the correlation of basement membrane collagenolysis with metastatic propensity. The c-Ha-ras oncogene alone, or combined with v-myc, transfected into early passage rat embryo fibroblasts, induce these cells to secrete high levels of type IV collagenolytic metalloproteinase and to concomitantly exhibit a high incidence of spontaneous metastases in nude mice. Cotransfection of c-Ha-ras plus the adenovirus type 2 Ela gene yields cells which are highly tumorigenic but nonmetastatic and fail to produce type IV collagenase. This effect is due to a suppression of collagenase elaboration, not increased production of a collagenase inhibitor, and not decreased production of a collagenase activator. Western immunoblots demonstrate a ten-fold or greater increase in the elaboration of latent type lV collagenase following ras transfection and suppression by Ela. These data support a bio- chemical linkage of type IV collagenase expression with the metastatic phenotype in this rodent system.